Is hand flapping a symptom unique to Autism Spectrum Disorder or can it be attributed to other conditions as well? A teen in the neighborhood mows several of the lawns and generally seems like a normal kid but a little odd. He doesn't seem to have many friends and is unusually shy, rarely introducing himself or striking up conversations on his own -- his parents or other people generally initiate. Once chatting he seems very intelligent, engaged, and even outgoing, but he also tends to avoid eye contact, is easily intimidated, and just seems a bit socially awkward for lack of a better description. And he flushes considerably when he's excited, upset, embarrassed, etc. His adoptive parents said he experienced some kind of trauma (abuse?) while with his biological parents, which largely makes sense. But he also does some kind of hand flapping when he's excited/nervous and doesn't realize anyone's looking. I thought that was a kind of "stimming" unique to Autism and, without intruding into their lives, am wondering if a difficult childhood could account for that or if there's necessarily more to the story.